SERTOLI. 417 



abundance of Serpulse in the aquarium house at the Zoological 

 Gardens, and the keeper is quite willing to give any advice, as to 

 the management of these interesting annelids. 



Supposing, then, that a group of Serpulse has been procured, it 

 should be placed in the aquarium close to the glass, and, if pos- 

 sible, the vessel should be one with flat sides, the ordinary fish- 

 globes giving a distorted image. A magnifying -glass should 

 then be fixed so as to command the orifices of the tubes, and all 

 will be ready. It is necessary to fix the glass, because the Serpu- 

 lse are strangely sensitive beings, and retreat into their tubes at 

 the slightest alarm. If even a hand be moved suddenly, though 

 at some little distance, the Serpulas shoot back into their tubes as 

 if propelled by springs, the feathery tentacles collapsing, and the 

 beautiful operculum closing up the entrance. 



This lightning-like rapidity of movement is caused by a won- 

 derful array of hooks on the front portion of the body. These 

 hooks are placed on the foot-warts which edge that part of the 

 body, and are wonderfully adapted for catching the membrane 

 that lines the tube. The botanist who looks at such a group as 

 is now before me in the microscope would be instantly reminded 

 of the seed-vessels of the " wait-a-bit" thorn, with its double array 

 of hooked prickles. Each hook is rendered still more effective 

 by the six or seven teeth into which its inner edge is cut, so that 

 the most formidable array of hooks that the ingenuity of anglers 

 ever devised, and named with appellatives as strange as their 

 shapes, would appear quite harmless by the side of the Serpula's 

 hooks, could they only be magnified to proportionate size. One 

 bunch of these most formidable hooks would seem to be all-suf- 

 ficient for the purpose, but when it is remembered that every foot- 

 wart has its hooked armatures, amounting to fourteen or fifteen 

 hundred in number, the power of the creature's hold ceases to be 

 surprising. 



Perhaps the reader may ask how the animal ever contrives to 

 push itself out of the case at all, seeing that it is held by such 

 a grasp. A farther look through the microscope shows that the 

 hooks are affixed to long tendinous bands, of great delicacy, but 

 at the same time of great strength, which enable the animal to 

 protrude the hooks so as to seize the membrane, and to with- 

 draw them when their purpose has been served. The dark back- 

 ground illumination shows the formation of the hooks in a very 

 clear and beautiful manner. 



D D 



